1. Technical Field
The present disclosure relates to a control mechanism of a discharge lamp, and more particularly, a method, a device and a system of controlling the discharge lamp for projection.
2. Description of Related Art
Present projection device products are full of diversities, a digital light processing (DLP) projection device, a liquid crystal projection device (LCD) and a reflective single-crystal silicon (LCOS) projection device are provided to different groups of consumers respectively. The digital light processing (DLP) projection device preferably uses discharge lamps generating light for projection, and more particularly, uses high-intensity discharge lamps (HID). In the digital light processing projection device, a color filter constructed by a color wheel with three primary colors of R, B, G (R for Red, B for Blue, G for green) rotates to pass light from light sources to sequentially generate beams of three primary colors and control spatial modulating elements simultaneously, thereby images are sequentially generated according to each of the three primary colors by time division, and color images are displayed. For a color filter of 3 colors, due to essential differences of various color lights and different requirements for brightness of various color lights, for example, if one of 3 colors appears again with different brightness comparing to other colors or if brightness in a specific image area is different from brightness in other image areas, then the requirement for the light intensity of the discharge lamp is different so that the required current of the discharge lamp is different. As shown in FIG. 1, FIG. 1 is a diagram of a discharge lamp current corresponding to each color of a color filter of 3 colors. As shown in FIG. 1, there are a difference ΔI between a discharge lamp current corresponding to B color and a discharge lamp current corresponding to R color and a difference ΔI′ between a discharge lamp current corresponding to B color and a discharge lamp current corresponding to G color. On the other hand, in FIG. 1, the operation that the discharge lamp current corresponding to R color changes to the discharge lamp current corresponding to B color and the operation that the discharge lamp current corresponding to B color changes to the discharge lamp current corresponding to G color both require for a certain time period, i.e., transition time periods tr, tf, in which a previous light color changes to a latter light color during the transition time period, i.e., the intensity of light emitted by the discharge lamp would change during the transition time. Since the intensity of light emitted by the discharge lamp would change during the transition time, the light emitted by the discharge lamp during the transition time is not used for projection in order to reduce influence on quality of image, and this will result in waste of energy. Therefore, the transition time is better to be shorter to enhance the efficiency of light emitted by the discharge lamp and to save energy as well.
Therefore, how to invent a method and a device for controlling a discharge lamp and to shorten a transition time during which a discharge lamp changes from one color to another color are problems that need to solve.